Can I map a key to do this job, so I just need to press once?
–
FreewindSep 2 '11 at 18:42

That is a key mapping. Emacs allows binding commands to key sequences and most commands are two keys. It's generally a bad idea to bind to one key since most of the one key bindings are taken by emacs fundamentals.
–
Ross PattersonSep 2 '11 at 18:46